A fast and non-destructive method is reported to nitrogen, phosphorus and potassium quantification in sorghum, oat, and maize residues. The reflectance spectra of 261 litter plant samples using near-infrared spectroscopy were obtained with integrating sphere and sampling rotator. Second derivative spectra and Partial Least Squares were used to develop calibration and validation models. The cross-validation (leave-one-out) technique was used to evaluate the performance of the calibration and validation models, based on analytical parameters, root-mean-square error of estimation, determination coefficient, number of latent variables, residual prediction deviation, root-mean-square error of cross-validation. It was concluded that near-infrared spectroscopy and chemometric tools are a fast and non-destructive alternative to determine nitrogen and phosphorus content in sorghum, oat, and maize residues using calibration and validation models developed according to values obtained from traditional chemical methods. For potassium content, the results indicate the low quality (imprecision) of the calibration and validation models.
The chemical composition of propolis is complex and varies according to location, seasonality, and vegetation where the hives are located. Raw and macerated propolis produced in different regions of Brazil were assessed and produced iPLS models from FTNIR combined to multivariate calibration to determine total phenolic content (TPC). The spectra of raw propolis were obtained analyzing samples directly, without treatment or processing, while macerated propolis was submitted to the milling process using liquid nitrogen. Concerning the results, the TPC ranged from 3.61 to 90.4 mg GAE g-1 , which indicates a significant difference among samples. It was possible to conclude that macerated propolis presented the best multivariate calibration obtained from the second derivative and SNV pre-processing. The error values RMSECV and RMSEP were 3.79 and 6.17 mg GAE g-1 respectively, while the determination coefficients in the calibration, cross-validation, and external validation were 0.97, 0.87, and 0.82, respectively.
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Las bayas Physalis, de la familia Solanaceae, han alcanzado una gran aceptación en todo el mundo debido al sabor de la fruta y su posible uso medicinal. Este estudio tuvo como objetivo evaluar la actividad antioxidante, las concentraciones de vitamina C, compuestos fenólicos y azúcares de frutas de dos especies de Physalis (Physalis pubescens L. y Physalis peruviana L.), así como sus variaciones durante el almacenamiento en dos temperaturas diferentes. El Physalis fue plantado en el oeste de Santa Catarina. Los frutos se cosecharon cuando las cápsulas eran de color amarillo pálido y luego se dividieron en tres grupos: frescos, refrigerados y congelados. Se evaluó el pH, sólido soluble totales, azúcares solubles totales, compuestos fenólicos, vitamina C y actividad antioxidante. Las frutas frescas de ambas especies presentaron mejores resultados para la mayoría de los parámetros analizados en comparación con las frutas refrigeradas y congeladas. La actividad antioxidante fue mayor en las frutas frescas para las dos especies de Physalis, experimentando una disminución cuando se acondiciona a bajas temperaturas. Los beneficios antioxidantes y los compuestos nutracéuticos se aprovechan mejor cuando las frutas se consumen frescas sin ningún proceso de almacenamiento a bajas temperaturas.
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